Tire uniformity is important for all tires, especially large off the road tires. One type of tire nonuniformity can occur in the tire carcass. For the green tire carcass, it is important that the carcass ply wire spacing be evenly distributed. It is further important that the liner gage be evenly distributed as well. Failure to meet specific uniformity criteria often results in the scrapping of tire carcasses, which can be expensive and wasteful. One cause of carcass nonuniformity may be attributable to the bladder shaping process. For very large radial tires, there tends to be a shape mismatch between the collapsed bladder and the green tire carcass. For example, prior to inflating the bladder, the collapsed outer diameter or circumference of the bladder used in the tire shaping process may exceed the inner diameter or circumference of the green tire. In addition, as the bladder is inflated, the bladder has an outer diameter much larger than the carcass inner diameter.
FIG. 1 illustrates a simplified schematic of a green carcass 30 with a folded bladder 40 inside. Certain edges 42 of the folded bladder are in contact with the inner surface 32 of the green tire carcass. The bladder edges have a tendency to grip the tire carcass, so that as the bladder is inflated, it results in the over stretching of the casing between the contact points and a localized thinning of the liner gauge. Once the overstretching occurs, the tire carcass must be scrapped. Thus an improved method and apparatus for shaping a large green tire carcass is desired, without any of the afore-mentioned disadvantages.